1. Field of the Art
The present invention relates generally to an electrically powered linear actuator and more particularly to an electrically powered actuator having an inline, direct motor mount and adapted for a variety of robotic or other applications. The invention has particular application to the control of robotic, pedestal or fixture welding guns and specifically, welding guns utilized in the automotive industry. The invention also has application to the actuation of clamping fixtures and the like in various industries such as the automotive industry.
2. The Prior Art
Various industries, and particularly the manufacturing industry, have utilized linear actuators to control the movements of automated welding guns, automated clamping fixtures, and the like. Specifically, in the automotive industry, actuation and control of welding guns and clamping fixtures has been accomplished using fluid actuators such as pneumatic or hydraulic actuators. While fluid actuators have functioned reasonably well for this purpose, they inherently embody various limitations. One, because of the possibility of leaks and failure of seals, etc. in the fluid actuators, there is always the concern of contamination of the worksite by a leaking fluid. Second, fluid actuators necessarily require a source of pressurized fluid and a fluid supply system. This leads to significant maintenance and other costs.
Accordingly, there is a need in the art for an improved actuator which overcomes the deficiencies and limitations of the prior art, and in particular, an improved actuator which is designed for use in controlling the movement of, and accommodating the loads associated with, welding guns, clamping fixtures and the like, such as those used in the automotive industry.
In contrast to the prior art, the present invention relates to an electric actuator having particular application to the actuation of welding guns, clamping fixtures or the like, and more particularly to the actuation of welding guns and clamping fixtures for use in the automotive manufacturing industry. In contrast to the fluid actuators of the prior art, the present invention provides an electrically powered in-line actuator which overcomes the limitations of the prior fluid actuators.
To minimize downtime and infra structure changes and the like during a changeover from existing fluid actuators to the electrically powered actuator of the present invention, the actuator of the present invention has been designed to fit within the same space or package and to be no heavier than existing fluid actuators, while at the same time providing at least comparable speed, thrust and range of movement. This is accomplished by utilizing a ball or roller screw electric actuator concept and by mounting the actuating motor in-line and directly to the actuator drive shaft. To provide additional advantages for maintenance or repair, the electric actuator of the present invention has also been designed to be comprised of a modular construction, thereby facilitating easy disassembly and substitution or repair of modular components.
To provide positioning accuracy to the actuator, a rotary or other similar encoder is provided. Like the motor, this encoder is provided in-line and in direct connection with the actuator drive shaft.
The actuator of the present invention also includes a means and mechanism for manually overriding the electrically powered actuator in the event of a loss of electrical power, actuator jamming or other actuator malfunction and a mechanism for enabling the actuator head and/or end cap to be rotated or mounted in a variety of different positions and/or configurations to accommodate different welding, clamping or actuation environments. In a preferred embodiment, a lubrication assembly is provided for insuring sufficient actuator lubrication and thus a reduction in maintenance. Means are also provided for accommodating the various loads (such as side loads) which are common with the actuation for welding guns and the like.
Accordingly, it is an object of the present invention to provide an improved actuator for welding guns, clamping fixtures and the like and more particularly for welding guns and clamping fixtures utilized in the automotive manufacturing industry.
Another object of the present invention is to provide an improved electrical actuator which can replace the conventional fluid actuators of the automotive manufacturing industry without sacrificing size or weight restrictions, while still maintaining comparable thrust, speed, range of movement and load accommodation.
A further object of the present invention is to provide an electric actuator having an in-line, direct motor mount and a manual override.
Another object of the present invention is to provide an electric actuator that eliminates or minimizes impact loading as the thrust tube reaches its innermost travel position.
Another object of the present invention is to provide an in-line electrical actuator in combination with an improved axial bearing retaining means.
A further object of the present invention is to provide an electric actuator with a thrust assembly bearing combination to resist side loads and to isolate the roller screw from any such side loads.
A still further object of the present invention is to provide an electrical actuator for use in the automotive manufacturing industry which provides for universal mounting arrangements.
A still further object of the present invention is to provide a lubrication system for the actuator.
These and other objects of the present invention will become apparent with reference to the drawings, the description of the preferred embodiment and the appended claims.